Physiological measurement of blood gases and hydrogen ion ( pH ) is very important for a variety of reasons. Myocardial contractility after cardiac surgery is strongly influenced by the acid-base balance. Patients with low cardiac output or with severe pulmonary disease show strong signs of acid-base imbalance due to changes in the peripheral circulation or in ventilation-perfusion relationships. Further, the optical determination or monitoring of blood oxygen and carbon dioxide saturation levels during certain medical procedures, such as critical cardiopulmonary and cardiovascular bypass heart surgery has numerous advantages. Equally important is the physiological measurement of pH in blood or serum along with oxygen for oxygen-heamoglobin dissociation circle and other diseases e.g. sickle cell anemia and malfunctions.
Fiber optic devices for measurement of blood gases, pH, electrolytes, and glucose are well known. Certain prior art sensors usually include an indicator molecule (dye) such as fluorescent or absorption dye which interacts with the component to be sensed or measured. Typically, an indicator, often in combination with an analyte permeable matrix, is a sensing element or a sensor means and is placed on or adjacent to a surface in the light path of the fibers. The interaction between the indicators and the component to be measured or sensed or analyzed is monitored utilizing signals carried by the fibers. Such a probe can be introduced into an artery to measure, depending on the type of dye molecule, various blood parameters such as pH, pCO2, and pO2. U.S. Pat. No. 4,682,895; 5,006,314; 4,974,929; 4,824,789; and European Patent Reference 0,352,610 describe various prior art probes.
It is a major aim of sensor/probe development to combine more than one sensor in a single probe so that a patient is not overtaxed with various probes introduced in his or her arteries. Such a combination or multiple sensor probe may, for example, contain pH, pO2, pCO2, and/or a stabilized element such as thermocouple wire.